1,3

a(n) is one fourth of the row product of the irregular triangle A281854.

Table of n, a(n) for n=1..64.

a(n) = A000010(A033949(n))/4, n >= 1.

EulerPhi@ Select[Range[2, 130], ! IntegerQ@ PrimitiveRoot@ # &]/4 (* Michael De Vlieger, Feb 02 2017 *)

Cf. A000010, A033949, A060679, A281854.

Sequence in context: A029235 A289052 A329046 * A106696 A131839 A143299

Adjacent sequences: A281853 A281854 A281855 * A281857 A281858 A281859

nonn

Wolfdieter Lang, Feb 02 2017

approved